With some careful planning and PCB trimming, Miguel managed to fit all the components needed for a 2.4 GHz ISM band spectrum analyzer into an old cellphone enclosure – resulting in an awesomely stealthy spy-worthy device.

The project uses a Nokia LCD (natch), an ATMega8 microcontroller, and a CYWM6935 wireless USB radio module – build documentation, schematic, and source files are available on Miguel’s site. [via Hack a Day]